A conventional cooling tower includes a cooling apparatus enclosed within a shell.
In a closed circuit cooling tower the cooling apparatus includes a cooling coil.
In a closed circuit cooling tower, the condenser water is pumped through a coil and water from an outside source is distributed over the coil to cool the water inside the coil.
In an open draft (induced draft) cooling tower the cooling tower does not include a coil.
In an open draft cooling tower, the water from the condenser is conducted straight up to the tower and is cooled by the air and the water distribution system of the cooling apparatus. The cooled water then returns to the condenser.
Specifically, in an induced draft cooling tower, a fan residing in the shell of the tower generates an air flow inside the shell to induce an airflow into the shell of the tower through passages defined in the sidewalls of the shell. A fluid, usually water, is pumped to the top of the cooling tower and distributed inside the shell typically through spray nozzles across the top of a fill media (fill cells). Fill cells are typically a bundle of spaced parallel plastic sheets supported inside the shell. Water is dispersed and downwardly passed by gravity over the fill cells. The large surface area of the fill cells, across which the water is dispersed, leads to the cooling of the water by the induced air flow between the fill cells. The cooled water is collected in a sump (pool) at the bottom of the shell and then returned to the cooling system of a facility, e.g. a building.
A heat exchanger may be provided beneath the fill cells. The heat exchanger may include coils. A fluid that is to be cooled is supplied to the coil at one end, and once cooled, the fluid exits at another end. Alternately, vapor could be supplied to the coil, condensed, and then collected. U.S. Pat. No. 7,484,718 is an example of a system as described and is incorporated herein by reference.
Cooling towers are usually deployed on building roofs. Thus, the weight of the tower is an important factor to consider when installing a cooling tower. Furthermore, since a typical rooftop has a limited area for a cooling tower, the footprint of a cooling tower is a factor to consider.
The known shell structures include cubical shells, cylindrical shells, and dome (semispherical) shells.
A cubical shell requires an inner frame for supporting the rectangular panels that form the cubical structure. Thus, cubical shells are heavy relative to their footprint. Furthermore, cubical shells have corners that tend to trap heated air and reduce the efficiency of the cooling tower.
A semispherical shell (e.g. a dome) occupies a large footprint relative to its height. For example, a hemisphere would have a circular base with a diameter that is twice its height (i.e. its radius). Thus, to increase the height of a cooling tower that has a semispherical shell, its footprint would have to be increased as well.
A cylindrical shell would also require an internal framework to support its flat top, which, like a cubical shell, would increase its weight relative to its footprint.
Different materials are known for the construction of shells including metals and plastic.